Merge pull request #9968 from emiljanitzek/feature/plugin-schema-type

fix: Add generic to plugin schema definition

Author: vkarpov15

index.d.ts

@@ -1123,7 +1123,7 @@ declare module 'mongoose' {
     pathType(path: string): string;
 
     /** Registers a plugin for this schema. */
-    plugin(fn: (schema: Schema, opts?: any) => void, opts?: any): this;
+    plugin(fn: (schema: Schema<DocType, Model<DocType>, SchemaDefinitionType>, opts?: any) => void, opts?: any): this;
 
     /** Defines a post hook for the model. */
     post<T extends Document = DocType>(method: MongooseDocumentMiddleware | MongooseDocumentMiddleware[] | RegExp, fn: (this: T, res: any, next: (err?: CallbackError) => void) => void): this;